1. Technical Field
The present invention relates to electrical connections to photovoltaic panels and more particularly to a junction box with upper and lower portions which snap together to achieve the electrical connection.
2. Description of Related Art
A photovoltaic module or photovoltaic panel is a packaged interconnected assembly of photovoltaic cells, also known as solar cells. Since a single photovoltaic module can only produce a limited amount of power, commercial installations include several modules or panels interconnected in serial and in parallel into a photovoltaic array. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired amount of current source capability. A photovoltaic installation typically includes the array of photovoltaic modules, an inverter, batteries and interconnection wiring. Electronic modules may be integrated with the photovoltaic modules which perform electrical conversion, e.g. direct current (DC) to direct current conversion, electrical inversion, e.g. micro-inverter, or other functions such as monitoring of performance and/or protection against theft.
Bus ribbon is a common interconnect that is used to connect photovoltaic modules. Bus ribbon is made up of a copper ribbon, or flat wire, that is coated in solder. The solder protects the surface of the copper from oxidation and provides a layer of solder to form the solder joint. Bus ribbon is generally 5 mm-6 mm wide, although some applications require bus ribbon to be more than twice as wide. Bus ribbon may serve as an input/output to a conventional junction box typically mounted on the back side of the photovoltaic module.
When part of a photovoltaic module is shaded, the shaded cells do not produce as much current as the unshaded cells. Since photovoltaic cells are connected in series, the same amount of current must flow through every serially connected cell. The unshaded cells force the shaded cells to pass more current. The only way the shaded cells can operate at a higher current is to operate in a region of negative voltage that is to cause a net voltage loss to the system. The current times this negative voltage gives the negative power produced by the shaded cells. The shaded cells dissipate power as heat and cause “hot spots”. Bypass diodes are therefore integrated with the photovoltaic modules to avoid overheating of cells in case of partial shading of the photovoltaic module.
Blocking diodes may be placed in series with cells or modules to block reverse leakage current backwards through the modules such as to block reverse flow of current from a battery through the module at night or to block reverse flow down damaged modules from parallel-connected modules during the day.
The term “wire” or “electrical wire” as used herein is a piece of metal or other electrically conductive material of any cross-sectional shape used for carrying electrical currents or signals. Bus ribbon is an example of an electrical wire used to electrically connect to photovoltaic panels.
The term “cable gland” as used herein refers to a device used for the entry of electrical cables or cords into electrical equipment and is used to firmly secure an electrical cable entering a piece of electrical equipment.